Playback apparatus and power-saving method

ABSTRACT

In a playback apparatus which plays back music in a plurality of audio formats, a control unit detects a voltage level of a power supply unit and restricts a playback of music in one of the audio formats, which requires power consumption whose amount exceeds a given value, when the detected voltage level is lower than a threshold value. Alternatively, the control unit restricts a playback of one of a plurality of pieces of music, which requires power whose amount exceeds a given value, when the detected voltage level is lower than a threshold value.

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application is based upon and claims the benefit of priorityfrom the prior Japanese Patent Application No. 2002-081917, filed Mar.22, 2002, the entire contents of which are incorporated herein byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to a playback apparatus for playingback music and a power-saving method.

[0004] 2. Description of the Related Art

[0005] Audio players that record digital audio data on a solid-statememory, a disk, etc. and play back the data have been used widely inrecent years. The digital audio data is compressed by digital datacompression technology. For example, all songs of one CD can be storedin a flash memory card whose storage capacity is much smaller than thatof the CD, and data of a plurality of CDs can be compressed and storedin a CD-R and reproduced therefrom.

[0006] Players using a flash memory card include a portable playerhaving a slot that is adaptable to an SD card, Smartmedia, compact flashand the like. Players using a CD-R include a portable player having botha CD player function and a playback function such as MP3 and WMA and aDVD player having an MP3 playback function.

[0007] Some audio players are adaptable to a variety of audio formats.They are able to select and reproduce any music that is stored in theaudio formats.

[0008] However, some audio players require a large amount of powerconsumption in decoding music data (including decompressing music data)according to the type of audio format. If a battery-powered portableplayer plays back music without taking consideration a difference inpower consumption between different audio formats, a battery will beexhausted at once. If, in particular, music that is stored in audioformat requiring a large amount of power consumption is played back witha small amount of remaining charge of a battery, the battery will beexhausted in a very short time.

[0009] In order to resolve the above problem, a technique to prevent abattery from being exhausted quickly and lengthen playing time while theremaining amount of charge of the battery is small is desired.

[0010] Jpn. Pat. Appln. KOKAI Publication No. 7-065507 discloses atechnique to lengthen the lifetime of a battery in a portable diskplayback apparatus. However, this technique aims at lengthening thelifetime of a battery used as a driving power supply by stopping a servocontrol operation during the stoppage of readout of data from arecording medium and does not refer to the problem of battery exhaustiondue to an audio format requiring a large amount of power consumption.

BRIEF SUMMARY OF THE INVENTION

[0011] Embodiments of the present invention provide a playback apparatuscapable of preventing a battery from being exhausted quickly andacquiring a longer playing time.

[0012] According to one aspect of the present invention, there isprovided a playback apparatus which plays back music in a plurality ofaudio formats, the apparatus comprising a voltage level detecting unitconfigured to is detect a voltage level of a battery; and a control unitconfigured to restrict a playback of music in, one of the plurality ofaudio formats, which requires power consumption whose amount exceeds agiven value, when the voltage level detected by the voltage leveldetecting unit is lower than a threshold value.

[0013] According to another aspect of the present invention, there isprovided a playback apparatus which plays back a plurality of pieces ofmusic, the apparatus comprising a voltage level detecting unitconfigured to detect a voltage level of a battery; and a control unitconfigured to restrict a playback of one of the plurality of pieces ofmusic, which requires power whose amount exceeds a given value, when thevoltage level detected by the voltage level detecting unit is lower thana threshold value.

[0014] According to still another aspect of the present invention, thereis provided a power-saving method applied to a playback apparatus whichplays back music in a plurality of audio formats, the method comprisingdetecting a voltage level of a battery; and restricting a playback ofmusic in one of the plurality of audio formats, which requires powerconsumption whose amount exceeds a given value, when the detectedvoltage level is lower than a threshold value.

[0015] Additional features and advantages of the invention will be setforth in the description which follows, and in part will be obvious fromthe description, or may be learned by practice of the invention. Thefeatures and advantages of the invention may be realized and obtained bymeans of the instrumentalities and combinations particularly pointed outhereinafter.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

[0016] The accompanying drawings, which are incorporated in andconstitute a part of the specification, illustrate embodiments of theinvention, and together with the general description given above and thedetailed description of the embodiments given below, serve to explainthe principles of the invention.

[0017]FIG. 1 is an external view of a music playback apparatus accordingto first and second embodiments of the present invention;

[0018]FIG. 2 is a block diagram showing an internal structure of themusic playback apparatus according to first and second embodiments ofthe present invention;

[0019]FIG. 3 is a block diagram illustrating functions of a control unitof the apparatus according to the first embodiment of the presentinvention;

[0020]FIG. 4 is a table showing a correspondence between an audio formatand power consumption in the apparatus according to the first embodimentof the present invention;

[0021]FIG. 5 is a table showing a correspondence between a thresholdvalue of battery voltage and that of power consumption in the apparatusaccording to the first embodiment of the present invention;

[0022]FIG. 6 is a flowchart illustrating a power-saving controloperation of the apparatus according to the first embodiment of thepresent invention;

[0023]FIG. 7 is a block diagram illustrating functions of a control unitof the apparatus according to the second embodiment of the presentinvention;

[0024]FIG. 8 is a table showing a correspondence between music, playingtime and amount of power in the apparatus according to the secondembodiment of the present invention;

[0025]FIG. 9 is a table showing a correspondence between a thresholdvalue of battery voltage and that of power consumption in the apparatusaccording to the second embodiment of the present invention; and

[0026]FIG. 10 is a flowchart illustrating a power-saving controloperation of the apparatus according to the second embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

[0027] Embodiments of the present invention will now be described withreference to the accompanying drawings.

[0028]FIG. 1 is an external view of a music playback apparatus accordingto the first and second embodiments of the present invention.

[0029] A music playback apparatus 1 is, for example, a portable playerand adaptable to different audio formats such as MP3, WMA and AAC. Themusic playback apparatus 1 is capable of playing back a plurality ofpieces of music in sequence. The apparatus 1 includes an operating unit11, a display unit 12, a speaker 13, a headphone terminal 14 and a slot15.

[0030] The operating unit 11 includes operating buttons to play back,stop, make a pause for, fast-forward and reverse a piece of music.

[0031] The display unit 12 is a display to display information aboutmusic to be played back.

[0032] The speaker 13 notifies a user of a given alert by voice when theuser performs an inadequate input operation.

[0033] The headphone terminal 14 is a terminal to which a headphone iselectrically connected in order to listen to music to be played back.

[0034] The slot 15 is a slot into/from which a memory card storing musicdata can be inserted/removed. When a memory card is inserted into theslot 15, music data is stored in a recording medium included in theapparatus.

[0035]FIG. 2 is a block diagram showing an internal structure of themusic playback apparatus according to the first and second embodimentsof the present invention.

[0036] The music playback apparatus 1 also includes a control unit 16, apower supply unit (battery) 17, a recording medium 18, a decoding unit19, a buffer memory 20, a D/A (digital/analog) converting unit 21 and aspeaker 22.

[0037] The control unit 16 controls the whole of the music playbackapparatus 1. For example, the control unit 16 performs processes ofreading music data out of the recording medium 18, decoding music datain the decoding unit 19, storing music data temporarily in the buffermemory 20 and transferring the data.

[0038] In particular, the control unit 16 (in the first embodiment) hasa function of detecting a voltage level of the power supply unit(battery) 17 and restricting a playback of music in audio formatrequiring power consumption the amount of which exceeds a given valuewhen the detected voltage level is lower than a threshold value. Forexample, the control unit 16 fulfills a function of inhibiting aplayback of music in the audio format or playing back only the beginningof music in the audio format.

[0039] The control unit 16 (in the second embodiment) has a function ofdetecting a voltage level of the power supply unit (battery) 17 andrestricting a playback of music requiring power whose amount exceeds agiven value when the detected voltage level is lower than a thresholdvalue. For example, the control unit 16 fulfills a function ofinhibiting a playback of the music or playing back only the beginning ofthe music.

[0040] The power supply unit 17 includes a battery that stores power.The unit 17 supplies power to the respective units of the music playbackapparatus 1.

[0041] The recording medium 18 corresponds to a flash memory card, aCD-R and the like. The medium 18 stores music data (audio data) andcontrol information associated with the music data.

[0042] The decoding unit 19 decodes music data read out of the recordingmedium 18 (the decoding includes decompression of compressed data). Thereadout operation is performed intermittently under the control of thecontrol unit 16.

[0043] The buffer memory 20 temporarily stores music data decoded by thedecoding unit 19. The buffer memory 20 absorbs a delay in music data inthe operation of reading data from the recording medium 18 and theoperation of decoding the data. The music data once stored in the buffermemory 20 is transferred to the D/A converting unit 21 at a constantdata transfer rate that is necessary for playing back the music data.

[0044] The D/A converting unit 21 converts music data output from thebuffer memory 20 from digital data to an analog signal.

[0045] The speaker 22 converts the analog signal output from the D/Aconverting unit 21 into an audible sound wave and outputs it. Thespeaker 22 corresponds to an internal speaker or an externally connectedheadphone.

[0046] (First Embodiment)

[0047] The music playback apparatus according to the first embodiment ofthe present invention will now be described.

[0048]FIG. 3 is a block diagram illustrating functions of the controlunit 16 of the apparatus according to the first embodiment.

[0049] The control unit 16 includes a main control unit 31 realized assoftware, a file table 32, a playback-capable/incapable determining unit33, an audio format/power consumption correspondence table 34, a batteryvoltage threshold value/power consumption threshold value correspondencetable 35, a voltage level detecting unit 36, a playback-incapablenotifying unit 37, a playback process control unit 38 and a sensor 39realized as hardware.

[0050] The main control unit 31 has a function of notifying theplayback-capable/incapable determining unit 33 of the contents (the typeof audio format for use) indicated in the file table 32 and inquiring ofthe unit 33 whether a playback can be performed or not when the musicplayback apparatus is put into playback mode.

[0051] Upon receiving a notification aboutplayback-capability/incapability of music for each audio format from theplayback-capable/incapable determining unit 33, the main control unit 31instructs the playback-incapable notifying unit 37 to make anotification about an unusable audio format and instructs the playbackprocess control unit 38 to control a playback process in a usable audioformat.

[0052] The file table 32 holds information (e.g., the type of audioformat and the number and playing time of each piece of music) aboutmusic data recorded on the recording medium 18. This information isreferred to by the main control unit 31 or theplayback-capable/incapable determining unit 33.

[0053] The playback-capable/incapable determining unit 33 forms on thetable 34 information about a correspondence between an audio format andpower consumption based on the contents of the file table 32 notified bythe main control unit 31.

[0054] The unit 33 has a function of determining which audio formatrequires power consumption whose amount exceeds a given value, withreference to the tables 34 and 35, when the voltage level of the batterydetected by the voltage level detecting unit 36 is lower than thethreshold value and then notifying the main control unit 31 of thedetermination result.

[0055] Referring to FIG. 4, the correspondence table 34 shows acorrespondence between a plurality of audio formats A to C used in thepresent apparatus and values D to F (D>E>F) of power consumptionobtained when music is played back in each of the audio formats. Forexample, the audio formats A to C include MP3, WMA, AAC (each using aspeech compression technique) and PCM (not using a speech compressiontechnique).

[0056] Referring to FIG. 5, the correspondence table 35 shows acorrespondence between threshold values X and Y (X>Y) of a plurality of(two) battery voltages that are preset as an index of reduction in theremaining amount of charge of the battery and values Z and W (Z>W) ofpower consumption that correspond to the threshold values. In this case,the values Z and W are set so as to satisfy the following relation:D>Z>E>W>F.

[0057] The voltage level detecting unit 36 detects a voltage level basedon the detection result received from the sensor 39 and sends dataindicative of the voltage level to the playback-capable/incapabledetermining unit 33.

[0058] The playback-incapable notifying unit 37 makes a notificationabout an audio format incapable of playback in response to aninstruction from the main control unit 31. This notification can bedisplayed through the display unit 12 shown in FIG. 1 or by voicethrough the speaker 13 concurrently with the display.

[0059] The playback process control unit 38 controls a playback processin audio format capable of playback in response to an instruction fromthe main control unit 31. The unit 38 does not play back music in theaudio format incapable of playback but skips it and sequentially playsback only the music in the audio format capable of playback.

[0060] The sensor 39 senses the remaining amount of charge (voltagelevel) of the battery of the power supply unit 17 and sends the sensingresult to the voltage level detecting unit 36.

[0061] A power-saving control operation of the apparatus according tothe first embodiment will now be described with reference to FIG. 6.

[0062] When the control unit 16 detects that the playback apparatus isset in playback mode in accordance with user's operation (step A1), itstarts power-saving control corresponding to the voltage of the battery.

[0063] First, the control unit 16 determines whether the voltage levelBL of the battery is lower than a first threshold value X (step A2).

[0064] If the control unit 16 determines that the voltage level BL isnot lower than the first threshold value X in step A2, a normal playbackis performed (step A3). On the other hand, if the voltage level BL islower than the value X, the flow advances to the next determinationprocess (step A4). In other words, the control unit 16 determineswhether the voltage level BL of the battery is lower than a secondthreshold value Y (step A4).

[0065] If the control unit 16 determines that the voltage level BL isnot lower than the second threshold value Y in step A4, the voltagelevel BL is expressed as follows: X>BL>Y (the remaining amount of chargeof the battery is small). Referring to each of the tables shown in FIGS.4 and 5, the control unit 16 determines that music in audio format A,which requires a larger amount of power consumption D than that of powerconsumption having a threshold value Z corresponding to the thresholdvalue X of battery voltage, is not played back and performs control toplay back music in audio format other than the audio format A (step AS).

[0066] If the control unit 16 determines that the voltage level BL islower than the second threshold value Y in step A4, the voltage level BLis expressed as follows: BL<Y (the remaining amount of charge of thebattery is very small). Referring to each of the tables shown in FIGS. 4and 5, the control unit 16 determines that music in audio formats A andB, which requires a larger amount of power consumptions D and E thanthat of power consumption having a threshold value W corresponding tothe threshold value Y of battery voltage, is not played back andperforms control to play back music in audio format other than the audioformats A and B (step A6).

[0067] According to the first embodiment described above, when theremaining amount of charge of a battery is decreased, the control unit16 restricts the playback of music in audio format having a large amountof power consumption in consideration of a difference in powerconsumption among audio formats. Thus, a playback can be stabilized whenthe remaining amount of charge of the battery is decreased and anavailable time of the battery can be lengthened. Since, moreover, aplurality of threshold voltages of the battery are set, the power-savingcontrol can be performed more finely and flexibly.

[0068] (Second Embodiment)

[0069] The music playback apparatus according to the second embodimentof the present invention will now be described.

[0070]FIG. 7 is a block diagram illustrating functions of the controlunit 16 of the apparatus according to the second embodiment of thepresent invention. The components common to those of the foregoing firstembodiment (shown in FIG. 3) are denoted by the same reference numerals.

[0071] The components different from those of the first embodiment(shown in FIG. 3) are a music/playing time/power amount correspondencetable 41 and a battery voltage threshold value/power amount thresholdvalue correspondence table 42.

[0072] In the second embodiment, the main control unit 31 has a functionof notifying the playback-capable/incapable determining unit 33 of thecontents (e.g., audio format and number, playing time and playing orderof music to be played back) shown in the file table 32 and inquiring ofthe unit 33 whether a playback can be performed or not when the presentapparatus is put into playback mode. Upon receiving a notification aboutplayback-capability/incapability of each piece of music from theplayback-capable/incapable determining unit 33, the main control unit 31instructs the playback-incapable notifying unit 37 to make anotification about music incapable of playback and instructs theplayback process control unit 38 to control a playback process for musiccapable of playback.

[0073] The playback-capable/incapable determining unit 33 forms on thetable 41 information indicative of a correspondence between music,playing time and amount of power based on the contents of the file table32 notified by the main control unit 31. In this case, an amount ofpower of each piece of music is calculated by the following equation:

(amount of power of music)=(power of audio format)×(playing time)

[0074] When a recording medium is changed or music data is added, anamount of power of new music is calculated appropriately and reflectedon the table 41. The calculation of the amount of power of music can beperformed by a unit other than the playback-capable/incapabledetermining unit 33.

[0075] The unit 33 has a function of determining which music requires anamount of power exceeding a given value, with reference to the tables 41and 42, when the voltage level of the battery detected by the voltagelevel detecting unit 36 is lower than the threshold value and thennotifying the main control unit 31 of the determination result.

[0076] Referring to FIG. 8, the correspondence table 41 shows acorrespondence between the numbers 1, 2, 3, 4, 5, . . . of music piecesto be played back in the present apparatus, the playing time of each ofthe music pieces and the amounts b, h, f, j, a, . . . (a >b>c>d>e . . .) of power used when the music pieces are played back.

[0077] Referring to FIG. 9, the correspondence table 42 shows acorrespondence between threshold values P and Q (P>Q) of a plurality of(two) battery voltages that are preset as an index of reduction in theremaining amount of charge of the battery and amounts R and S (R>S) ofpower that correspond to the threshold values. In this case, the amountsR and S of power are set so as to satisfy the following relation:a>R>b>S>c.

[0078] As in the first embodiment, the voltage level detecting unit 36detects a voltage level based on the result of detection received fromthe sensor 39 and sends data indicative of the voltage level to theplayback-capable/incapable determining unit 33.

[0079] The playback-incapable notifying unit 37 makes a notificationabout music incapable of playback in response to an instruction from themain control unit 31. This notification can be displayed through thedisplay unit 12 shown in FIG. 1 or by voice through the speaker 13concurrently with the display.

[0080] The playback process control unit 38 controls a playback processof music capable of playback in response to an instruction from the maincontrol unit 31. In this case, the unit 38 does not play back musicincapable of playback but skips it and sequentially plays back only themusic capable of playback.

[0081] As in the first embodiment, the sensor 39 senses the remainingamount of charge (voltage level) of the battery of the power supply unit17 and sends the sensing result to the voltage level detecting unit 36.

[0082] A power-saving control operation of the apparatus according tothe second embodiment will now be described with reference to FIG. 10.

[0083] When the control unit 16 detects that the playback apparatus isput into playback mode in accordance with user's operation (step B1), itstarts power-saving control based on the voltage of the battery.

[0084] First, the control unit 16 determines whether the voltage levelBL of the battery is lower than a first threshold value P (step B2).

[0085] If the control unit 16 determines that the voltage level BL isnot lower than the first threshold value P in step B2, a normal playbackis performed (step B3). On the other hand, if the voltage level BL islower than the value P, the flow advances to the next determinationprocess (step B4). In other words, the control unit 16 determineswhether the voltage level BL of the battery is lower than a secondthreshold value Q (step B4).

[0086] If the control unit 16 determines that the voltage level BL isnot lower than the second threshold value Q in step B4, the voltagelevel BL is expressed as follows: P>BL>Q (the remaining amount of chargeof the battery is small). Referring to each of the tables shown in FIGS.9 and 8, the control unit 16 determines that music of No. 5, whichrequires a larger amount a of power than that of power having athreshold value R corresponding to the threshold value P of batteryvoltage, is not played back and performs control to play back musicother than the music of No. 5 (step B5).

[0087] If the control unit 16 determines that the voltage level BL islower than the second threshold value Q in step B4, the voltage level BLis expressed as follows: BL<Q (the remaining amount of charge of thebattery is very small). Referring to each of the tables shown in FIGS. 9and 8, the control unit 16 determines that music of Nos. 5 and 1, whichrequires larger amounts a and b of power than that of power having athreshold value S corresponding to the threshold value Q of batteryvoltage, is not played back and performs control to play back musicother than the music of Nos. 5 and 1 (step B6).

[0088] According to the second embodiment, when the remaining amount ofcharge of a battery is decreased, the control unit 16 restricts theplayback of music requiring a large amount of power in consideration ofa difference in amount of power among music pieces. Thus, a playback canbe stabilized when the remaining amount of charge of the battery isdecreased and an available time of the battery can be lengthened. Since,moreover, a plurality of threshold voltages of the battery are set, thepower-saving control can be performed more finely and flexibly.

[0089] The present invention is not limited to the forgoing embodiments.For example, the power-saving control of the first embodiment and thatof the second embodiment can be combined with each other.

[0090] According to the playback apparatus of the present inventiondescribed above, the battery can be prevented from being exhausted in avery short time and a longer playing time can be obtained.

[0091] Additional advantages and modifications will readily occur tothose skilled in the art. Therefore, the invention in its broaderaspects is not limited to the specific details and representativeembodiments shown and described herein. Accordingly, variousmodifications may be made without departing from the spirit or scope ofthe general inventive concept as defined by the appended claims andtheir equivalents.

What is claimed is:
 1. A playback apparatus which plays back music in aplurality of audio formats, the apparatus comprising: a voltage leveldetecting unit configured to detect a voltage level of a battery; and acontrol unit configured to restrict a playback of music in one of theplurality of audio formats, which requires power consumption whoseamount exceeds a given value, when the voltage level detected by thevoltage level detecting unit is lower than a threshold value.
 2. Theplayback apparatus according to claim 1, further comprising: a firststorage unit configured to store first information indicating acorrespondence between the plurality of audio formats and powerconsumption; and a second storage unit configured to store secondinformation indicating a correspondence between a threshold value of thevoltage level and a threshold value of the power consumption, whereinthe control unit determines an audio format which is to restrict aplayback of music using the first information and the secondinformation.
 3. The playback apparatus according to claim 2, wherein thesecond information indicates a plurality of correspondences havingdifferent threshold values.
 4. The playback apparatus according to claim1, wherein the control unit makes a notification of information about anaudio format which restricts a playback of music by one of display andvoice.
 5. The playback apparatus according to claim 1, furthercomprising: means for storing first information indicating acorrespondence between the plurality of audio formats and powerconsumption; and means for storing second information indicating acorrespondence between a threshold value of the voltage level and athreshold value of the power consumption, wherein the control unitincludes means for determining an audio format which is to restrict aplayback of music using the first information and the secondinformation.
 6. The playback apparatus according to claim 5, wherein thesecond information indicates a plurality of correspondences havingdifferent threshold values.
 7. The playback apparatus according to claim1, wherein the control unit includes means for making a notification ofinformation about an audio format which restricts a playback of music byone of display and voice.
 8. A playback apparatus which plays back aplurality of pieces of music, the apparatus comprising: a voltage leveldetecting unit configured to detect a voltage level of a battery; and acontrol unit configured to restrict a playback of one of the pluralityof pieces of music, which requires power whose amount exceeds a givenvalue, when the voltage level detected by the voltage level detectingunit is lower than a threshold value.
 9. The playback apparatusaccording to claim 8, further comprising: a first storage unitconfigured to store first information indicating a correspondencebetween the plurality of pieces of music and an amount of power; and asecond storage unit configured to store second information indicating acorrespondence between a threshold value of the voltage level and athreshold value of the amount of power, wherein the control unitdetermines a piece of music whose playback is to be restricted using thefirst information and the second information.
 10. The playback apparatusaccording to claim 9, wherein the control unit calculates an amount ofpower of each of the plurality of pieces of music from playing time ofeach of the plurality of pieces of music.
 11. The playback apparatusaccording to claim 9, wherein the second information indicates aplurality of correspondences having different threshold values.
 12. Theplayback apparatus according to claim 8, wherein the control unit makesa notification of information about a piece of music whose playback isto be restricted by one of display and voice.
 13. The playback apparatusaccording to claim 8, further comprising: means for storing firstinformation indicating a correspondence between the plurality of piecesof music and an amount of power; and means for storing secondinformation indicating a correspondence between a threshold value of thevoltage level and a threshold value of the amount of power, wherein thecontrol unit includes means for determining a piece of music whoseplayback is to be restricted using the first information and the secondinformation.
 14. The playback apparatus according to claim 13, whereinthe control unit includes means for calculating an amount of power ofeach of the plurality of pieces of music from playing time of each ofthe plurality of pieces of music.
 15. The playback apparatus accordingto claim 13, wherein the second information indicates a plurality ofcorrespondences having different threshold values.
 16. The playbackapparatus according to claim 8, wherein the control unit includes meansfor making a notification of information about a piece of music whoseplayback is to be restricted by one of display and voice.
 17. Apower-saving method applied to a playback apparatus which plays backmusic in a plurality of audio formats, the method comprising: detectinga voltage level of a battery; and restricting a playback of music in oneof the plurality of audio formats, which requires power consumptionwhose amount exceeds a given value, when the detected voltage level islower than a threshold value.